well, the mri/mra would have shown a developing aneurysm, or avm. an arterial vein
malformation gives off symptoms like a cva. so does an aneurysm, in any case the mri scan would have definitely picked it up. an aneurysm is a balooning of an artery in many levels, there can be a dissecting, that is whenit forms a pseudolumen,which fills with blood.